Create `shortcuts.html` as a standalone reference page.
Implement `#shortcuts-modal` in `index.html` to display key bindings.
Implement `#guide-modal` with an iframe to embed `User_Manual.html` directly in the app.
Refactor header navigation into color-coded buttons (Green/Blue/Amber-Indigo).
Update `src/dom.js` and `src/ui.js` to handle modal visibili and interactions (ESC key, 'k' key, click-to-close).
Improve visual consistency of header button heights and moda styling.
RUSHIL AMBARISH KADU